The present invention relates to cardiopulmonary diagnostics. More specifically, the present invention relates to a data acquisition and timing method and apparatus by which pulmonary capillary pressure may be more readily obtained utilizing known curve fitting techniques such as Gaar""s equation.
Pulmonary capillary pressure, the blood pressure in the capillaries between the pulmonary artery and the pulmonary vein, is long known as a useful indication of fluid balance in a patient. The measure is particularly useful in patients with sick lungs because the pressure of the blood in the capillaries of the lungs defines the driving force pushing fluid out of the blood and into the air sacs, potentially causing pulmonary edema. Under the current state of the art, pulmonary capillary pressure is obtained by inserting a balloon flotation catheter, such as the well-known Swan-Ganz type flow-directed catheter, through the heart and into a smaller branch of the pulmonary artery. Once the catheter is in place, a balloon at the distal tip of the catheter is inflated to occlude blood flow through the branch. The resulting decaying pressure curve downstream the balloon occlusion is then measured by a data acquisition device, and is thereafter utilized to estimate the pulmonary capillary pressure with well known compartment model formulas such as Gaar""s equation.
Unfortunately, the conventional method for obtaining capillary pressure presents significant risk to the patient. Inflation of the catheter""s balloon within the pulmonary artery causes a distinct force to be exerted outwardly against the artery""s interior wall. A naturally fragile or otherwise weakened artery may not tolerate this outward force, resulting in rupture of the artery. Although not extraordinarily common, the ultimate effect of a ruptured artery is catastrophic to the patient; a surgical team has only between about 30 seconds and three minutes to open the patient""s chest and clamp the bleeder before the patient bleeds to death into the plural cavity. To compound the problem, pulmonary artery catheters have a tendency to migrate downstream. As the catheter enters smaller and smaller portions of the arterial branch, the chance for rupture of the artery increases. Because of these inherent risks, it is very important that the measurement not be unnecessarily repeated. Unfortunately, however, clinicians must often repeat the measurement because unless the occlusion takes place during the systolic upstroke it is not readily possible to determine the exact time of occlusion -an important input parameter for the compartment models.
It is therefore a specific object of the present invention to obtain an estimate of the pulmonary capillary pressure without need for unnecessary inflation of a pulmonary artery catheter balloon.
In accordance with the foregoing objects, the present invention generally comprises a medical device for triggering the inflation of a pulmonary artery catheter balloon. The device generally comprises a waveform analysis machine which monitors the pulmonary artery blood pressure waveform and triggers the inflation of the catheter balloon at such a time as to cause occlusion of the pulmonary artery during the systolic upstroke. The time of occlusion is then readily apparent in the resulting decaying blood pressure waveform, which may then be used as a basis for compartment model estimation of the pulmonary capillary pressure.
Many other features, objects and advantages of the present invention will be apparent to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims.